Horizontal ELV Launchpad

guest blogger john hare

A recent discussion mentioned that some ELVs are launching with a T/W ratio of 1.15 or less. An ongoing discussion concerns the cost and limitations of launch pads for them. Space advocates like us would mostly like a wider variety of launch locations than the fixed launch pad facilities allow. Using available runways is a popular thought. It might be possible to dispense with the vertical launch pads, save money, and gain a little performance in the bargain.

It has been suggested many times that a launch sled would benefit HTHL RLVs. It seems possible that a launch sled set up might assist almost unmodified current ELVs. The flame containment of vertical launch could be exchanged for a few hundred feet of relatively inexpensive runway flame protection. The vehicle could accelerate at 8-9 meters per second instead of 1.5 in the initial 20 or so seconds. The ELV could abort if a problem is discovered in the first 15 seconds of full thrust.

A small ski ramp used in the same manner as the small British aircraft carriers for Harriers could start the turn vertical at the end of the runway. TVC could complete the turn as the sled dropped off keeping most of the velocity gained in the horizontal. The sled would provide structural support for the relatively fragile stack until it is in a stable trajectory. Considering the weight of the sled, the stack could accelerate to 160 m/s in the first 20 seconds instead of 30 m/s in a vertical launch. While there would be losses in the turn, net gain should be over 100 m/s for the stage. At the sharp end, this is somewhat useful. Canard wings at the front of the sled could assist the vertical maneuver.

Justification for the cost of this system could only be if it was weighed against building a new launch pad. If you have an existing one, or your vehicle doesn’t require a pad in the first place, the expense wouldn’t be justified. The development cost of a new way of launching could also be prohibitive.

Launch pad cost, launch pad availability, abort options, and slight performance gain could make this a concept worth consideration.

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johnhare

johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
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johnhare

About johnhare

I do construction for a living and aerospace as an occasional hobby. I am an inventor and a bit of an entrepreneur. I've been self employed since the 1980s and working in concrete since the 1970s. When I grow up, I want to work with rockets and spacecraft. I did a stupid rocket trick a few decades back and decided not to try another hot fire without adult supervision. Haven't located much of that as we are all big kids when working with our passions.
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41 Responses to Horizontal ELV Launchpad

  1. Karl Hallowell says:

    I understand the MX missile had some sort of steam launch design. In addition to clearing the tower/silo and providing a bit of initial velocity, it allowed you to reuse the launchpad quickly.

    Your sled idea is interesting. It eliminates about half of the gravity losses from the first 20 seconds when the rocket leaves the track. If it can be made more efficient, you probably could recover most of the gravity losses. Another nice feature is that this can transition into an assisted launch system.

    Have some sort of EM rail accelerate the rocket and light it. If you maintained the current launch profile except that the rocket ignited as it left the track, then you’d add 30 m/s to the launch delta v. Hmmm, not as good as I thought. Interesting that the horizontal sled provides almost as much delta v for the rocket as if you had pushed the sled along. That’s a result of the low thrust/weight engines.

    One problem I see is that air resistance goes up significantly. I don’t know how much you would lose in delta v as a result.

  2. Eric Collins says:

    I think Karl may have a point about resistive losses. There’s the rolling/sliding resistance of the sled, and increased drag during the pitch-up maneuver. Assuming that you want to keep the horizontal velocity obtained on the sled, then there is also going to be additional drag due to flying at lower angle of attack through the lower atmosphere. In other words, you’ll probably take longer to get up out of the thickest part of the atmosphere, and you’ll probably be exposing more cross-sectional area while you’re in this part of the flight. Plus flying at a lower angle of attack means that the rocket’s center of gravity is no longer directly over the engines. Thus, the rockets can no longer deliver 100% of their thrust in the longitudinal direction. Part of the thrust must be used to keep the nose from dropping.

    Alternatively, if you plan to pitch-up to vertical after leaving the sled, then you will effectively loose all of the horizontal velocity due to drag on the rocket as it translates. In which case, what have you really gained by launching horizontally?

    Of course there are the structural issues to be considered. I’m not sure how much lateral loading that existing rockets would be able tolerate. The thrust structures are designed to take most of the load in the longitudinal direction. In addition to taking the load lying on their side, fully fueled, they also have to survive a rather sudden pitch-up maneuver. To make this work, you may end up paying a slight mass penalty for more robust structures.

    I do like the ability to safely abort up to a point. Perhaps it might be better to consider the same approach, but in a vertical shaft rather than on a horizontal runway. I know part of you argument was to avoid having to build a launch pad and flame trench, but if you think about it, building a couple miles of sled track is not going to be a picnic either.

    FWIW

  3. Adam Greenwood says:

    If there were more of a market, this is the kind of incremental improvement that would make sense. Hopefully the suborbital guys and COTS are able to incrementally make the market.

  4. gravityloss says:

    All kinds of fancy loads on the fully fueled rocket when it makes the curve at high speed…

    An air launch wing platform would make more sense in my view.

  5. Tom D says:

    It seems like you would need to add a wing (and all of the weight and complexity that adds) to the vehicle to go all the way from horizontal to vertical. I think air launch looks more promising in the near term.

  6. David Summers says:

    Well, it’s not that bad – the sled could provide the necessary support structure to keep the thing from breaking during the turn, and the sled doesn’t need to leave the ground. I see 2 issues with this approach:

    1) In order to maximize the velocity gain and minimize the changes to the rocket, the ramp should end in an almost vertical attitude – that would make it substantially harder to modify existing airports to handle the system.
    2) The rocket needs to “stage” from the sled – staging events are inherently risky. Basically, clearing the tower risk has been traded for clearing the sled risk.

    Probably a net gain – the question is: “Is the gain worth it?”

  7. How fast would you be going when you hit the ski ramp? 160m/sec? (345 mph).

    Would the vehicle be able to take the stresses of the ramp? I’m assuming a very short ramp, based on your aircraft carrier analogy.

  8. “”””””Have some sort of EM rail accelerate the rocket and light it.””””””

    Why not a rocket sled? A rocket sled at China Lake accellerated the empty 1st stage of the Saturn V to Mach 4.5 back in the 60’s.

    Of course, the ski ramp concept won’t do if you are accellerating to high speeds. How fast were you envisioning the assist phase to be, Karl?

  9. Tim Christianson says:

    Interesting you bring this topic up. Some other people have been working on this for a long time.
    Check out http://www.g2mil.com/skyramp.htm

    They used to have their own website called http://www.skyramp.org, but that was shut down last year.
    I thought the most interesting concept of theirs to try out, would be to take a Spacex Falcon I on top of a small mountain and see how the altitude affected the rockets performance. They believed the rocket would be able to carry more payload. It would be interesting to see the results.

  10. Robert Lynn says:

    How about the side of Chimborazzo in Equador:
    http://en.wikipedia.org/wiki/Chimborazo_(volcano)
    This peak is furthest point from earth’s core.

    Run two sets of railway lines up steep western side starting at 4000m and reaching 6500m, angle about 30degrees.

    Why two sets of rails? Well you can have a big pulley block at top and a thousand tonne railcar plumetting down the second set to accelerate the LV up to say 4-500m/s at the top.

    Ambient pressure less than half an atmosphere allows a higher ISP nozzle + much reduced drag losses from altitude launch. But you can still do almost all the vehicle work at a very livable altitude of 3500-4000m.

    4-500m/s is a big delta V saving and being on the equator is great for launch inclination flexibility.

    Cost: 10km of high quality rail + some roads and facilities in a low labour cost country that would probably bend over backwards for the high tech industry it would bring. Don’t need to pay for high powered motors to do the accelerating.

    Overall it might effectively knock 1km/sec off the delta V requirement (including higher isp nozzles), or maybe double payload capacity for a given LV.

    PS: As an ex alt.spacer of the 90’s it’s nice to find a site that captures that spirit. Keep it up!

  11. David Wenzel says:

    I tend to agree with gravityloss. By the time you’ve modified a runway, rocket, etc. you’d almost certainly be better off using a very large carrier aircraft – super-sized WKII or a heavily modified old 747. This gives you at least as much velocity, gets the stack above the thickest air – reducing friction losses and stresses during transition to vertical, can provide the translation to near vertical before releasing the stack (avoiding the need for wings on the rocket), and allows you to use any number of airports with few if any mods. Like WKII, the key to economies is finding plenty of activities to allow the carrier to cover its operating costs and pay back it’s development (or purchase) cost. An EM sled sounds a nice idea if you want to throw large amounts (in small frequent parcels) of dumb mass into orbit, but would cost billions to develop, build and operate (as proven by maglev trains to date). Now, if you were creative, you could combine a 10-20km length of maglev train track running roughly West/East with a short dedicated “side-track” that ends in a ski-ramp section, and when you’re not firing payload into orbit, most of your track will be gainfully employed transporting people… just make sure you change the points after you launch your payload, or the next train will turn into one hell of a roller-coaster!

  12. The Germans launched V1 buzz bombs this way.

    I think the ski jump ends up dominating the design. At e.g. 130 m/s, a 1.5 G rotation has a radius of 34 kilometers — because 1 G of that is the force of gravity. I don’t think you are going to get much rotation from your sled path.

    To reduce the path curvature, have the sled run up a small hill. If the climb angle is 30 degrees, and the rocket thrust is 1.15x weight, then it will accelerate up the hill at 0.65 G. After 21 seconds, it will be going 143 m/s and have covered 1.5 km. The vertical component of that velocity will be 72 m/s.

    If instead the same rocket accelerates straight up for 21 seconds at .15 G, it will be going 41 m/s.

    So, then sled gets you a bonus of 31 m/s of vertical velocity. The horizontal velocity is fine, although a fair portion of it will bleed off as drag. The bigger problem is that your rocket nozzle is not pointed down, so that the thrust lifting away from earth is only sin(slope) times the rocket thrust. This means that you’ll be losing vertical velocity until a combination of rotation and loss of mass gets the vertical thrust component larger than the gravitational force.

    The big benefit of sled launch, however, is being able to start with more gas in the tank. Vertical launches require thrust-to-weight be greater than 1. Starting with some vertical velocity means you can start at a lower thrust-to-weight ratio… which gives a larger mass ratio, which gives a larger delta-V.

    I’m going to guess that you want a pretty steep ramp, something like 45 degrees or more: http://spreadsheets.google.com/ccc?key=p23gSOFoUMd3U1kI2ASSLCQ

    I’d expect a little more analysis to show the following:
    – You will want to curve the track so the rocket sees something like a constant 1.5 Gs of cross-axis loading. This will avoid some gravity losses at the beginning, get the benefit of pitch-up at the end, and keep the structural loads low. Even though you can have a tighter curve at low velocities, I suspect you’ll end up with relatively little benefit from the curvature.
    – You will want to start with a thrust-to-weight ratio of something like 1.05.
    – You don’t want canards or wings. A little attack angle on the way up will do just fine.

    If you want a simple stage zero that gives even more oomph, how about a hot water rocket? http://ambivalentengineer.blogspot.com/2006/02/catapult-gain.html and http://ambivalentengineer.blogspot.com/2006/05/three-stage-to-orbit.html

  13. CFE says:

    It’s not a bad idea, but it does pose a lot of tough challenges. My biggest concern would be the additional drag losses incurred by flying a depressed trajectory through the dense lower atmosphere. That’s one of the key selling points to the Pegasus approach: fly to the thinner atmosphere around 40kft and cut ‘er loose.

  14. john hare says:

    Air launch does make more sense for the vehicles that can be lifted by aircraft with only minor modification. The Atlas class is a bit large for that application. Building a WK heavy specifically to launch inherently low flight rate ELVs sounds like a really poor business case to me. Only if there are other revenue sources for the specialty aircraft would it make sense.

    EM tracks and long specialized ramps up mountains would seem to be fairly expensive solutions compared to using the same money to develop a high flight rate RLV. I’m still brainstorming cheap rather than best. Trading a specialized launch pad for a rolling sled seems like a possible way to gain a bit of performance while saving infrastructure costs, with abort possibilities as a bonus.

    I picture the ramp as 5 degrees or so, just enough to get the vertical turn started and avoid controlled flight into terrain. After leaving the ramp, an aerodynamic turn to vertical with the TVC providing the control function should convert much of the horizontal velocity to vertical. Side structural loads on the vehicle are a serious issue, the sled may have to remain attached during the turn for structural support. This creates a staging event before the sled parachutes home, which could be a problem.

    The sled could clearly become a zero stage with a water or steam rocket. My preference would be enough liquid fueled combustion rocket to provide 1.5 gee or so down the runway with subsonic separation after the vertical turn. Again it becomes a cost issue

  15. Eric Collins says:

    The staging event may not be as bad as you may think. After the pitch up maneuver begins with the TVC, just allow the track and sled to slowly drop away, like a car cresting a hill. If the TVC on the rocket is capable of completing the pitch up on its own, then it should cleanly separate from the sled as the track begins to curve away. If anything goes wrong, you can still kill the engines, and let the rocket lay back down on the sled which would then coast or brake to a stop. This would require a good deal more open ground (and a long gently rolling hill) for the track, but it should be a fairly benign separation.

  16. I used to be a regular correspondent with the SkyRamp site, and always found the concept intriguing.

    The problem with mountain launch is that, well, you have to find an ideal mountain. It has to be reasonably accessible, allow for a more or less easterly launch, and — by the time you find such a mountain — it turns out to be the last habitat of the Mexican Rotweiler Squirrel.

    An ideal mountain allows for at least 2.5 miles of track up approx. a 40-45 deg. inclination, and that’s assuming you want to do 6 g’s accelleration to get to Mach 2.

    The only truly available mountain may be maturango Peak on the China Lake site. It is good for maybe a mile-long track at an ideal angle. It could be used for really high-G unmanned payloads. Of course, they could build a long, tapered berm to make the track a lot longer with a shallower inclination, like 25-30 deg.

    WOuldn’t the NM Spaceport or its vicinity be another candidate for higher-altitude ground launches or even mountainside launches?

  17. Another option might be a “virtual rail launch,” where a high accelleration, short duration booster could be used to reach fairly high speeds (Mach 1.5 to Mach 2), over a relatively short distance in a vertical launch. The advantage would be that such a booster could be relatively small, and would be recovered virtually on site by parachute, or even vertical landing system.

    For instance, a 5g accelleration rate for, what, 3.5-4 miles for Mach 2? If you brake it’s forward/upward momentum after separation, it could be recovered 8-10 miles downrange, at most.

  18. Incidentally, John, your concept presented here reminds me of the HOTOL concept, where the HOTOL would be launched off a conventional runway with a rocket/jet-powered wheeled carrier.

  19. john hare says:

    on 28 Jan 2009 at 2:16 pm18Roderick Reilly

    Incidentally, John, your concept presented here reminds me of the HOTOL concept, where the HOTOL would be launched off a conventional runway with a rocket/jet-powered wheeled carrier.

    The first mention of the concept I know of is from Sanger from the early 1940s. Many RLVs have suggested this. This twist is just a possibility to get a little more use from existing hardware.

  20. Robert Lynn says:

    Reading through the skyramp site is interesting, though from an engineer’s standpoint some of the info is a bit garbled, it does however make a good case.

    We can build large tunnels for about $20million per mile (eg 6 mile long 10m dia Manapouri hydroelectric tailrace tunnel completed 10 years ago for about 100 million). So if we want to dig a 4 mile long 14m diameter tunnel at a 45 degree angle from near the peak of a tall mountain it should be feasible to complete it for a billion, including all infrastructure required. Deepest mines are currently getting near 2.5 miles.

    You would then have a cheap to maintain asset that can potentially be used forever as a low cost first stage for all ELV’s and RLV’s.

    Given existing LV expenditures this seems like a pretty good investment.

    China is ideally set up to do this with all the 7000m+ mountains in Tibet.

  21. David Summers says:

    Mr. President! We cannot allow a launch shaft gap!

  22. Jonathan Goff Jonathan Goff says:

    David,
    Ugh. That was painful. 🙂

    What did we do to deserve such pun-ishment?

    ~Jon

  23. “””””””We can build large tunnels for about $20million per mile (eg 6 mile long 10m dia Manapouri hydroelectric tailrace tunnel completed 10 years ago for about 100 million). So if we want to dig a 4 mile long 14m diameter tunnel at a 45 degree angle from near the peak of a tall mountain “””””””””

    At about 4 Gs accelleration, that would be Mach 2.1 at exit from the tunnel mouth. Mach 2.4 at 5 Gs. Assuming a partially evacuated tunnel and air density on the peak at less than half of sea level, you should be able to get to LEO in a single stage, don’t you think?

    Thing is, you’re looking at at least a 16,000 ft peak to make a 4-mile tunnel feasible at 45 deg. angle. No such animal in N. America.

  24. Roger Strong says:

    If it’s that hard do find an ideal mountain, it might be easier to find an ideal mining project that you could share costs with.

    Check out this illustration of INCO’s Creighton mine near Sudbury, Ontario – following a vein of ore downward at a roughly 45-degree angle. That’s the Sudbury Neutrino Observatory in the bottom right corner, 2km below ground, saving money the same way.
    http://www.sno.phy.queensu.ca/images/mine.GIF

    If you can’t find an ideal mine, with a vein running downward in the right direction, perhap you can convince someone to dig your tunnel as an equipment access / air / escape shaft.

  25. Robert Lynn says:

    Mt Logan at 20000ft has a roughly 35 degree western flank dropping to about 10000 ft. Though it is pretty close to alaska.

    I do agree though, Ecuador, Kenya and Tibet are far better prospects, though hawaii coul be OK too.

    A 2000ft radio mast in North Dakota cost $3million in inflation adjusted dollars (0.5m in 1963), and the Berj scyscraper is now 2700ft. Given the benefits of altitude maybe “up” would be cheaper and more useful than “down”, or perhaps a combination of the two?

    A mast a mile or two tall with adjoining a hole 2 miles deep and a 5g super elevator would be a pretty solid tourist attraction; viewing and base jumping. Plus with a good winch/elevator you could make 40-50 second zero-g rides.

    So anybody got a couple of hundred million langushing?

  26. john hare says:

    A launch loop might be an economical way to get the few kilometer long track in place, at least compared to tunneling in foreign mountains and such. For the performance gain discussed though, a RTLS rocket zero stage is almost certainly cheaper and more flexible. Don’t take my word for it though, give Jon a couple of Dirksens and see what he can deliver.

  27. Roger Strong:

    Yes, mine pits were something I discussed at length with the SkyRamp site guy.

    Robert Lynn:

    Also discussed tall launch towers at SkyRamp. Even the Saturn V tower was tall enough for a 100-150 mph boost.

    A radio-tower tall launcher for small vehicles using a high-G rate could impart better than Mach 1 speeds, I would think.

    For instance, using the 2000 ft. tower example: a sounding rocket propelled at 8 Gs accelleration would hit about Mach 1.6 as it leaves the tower. If the tower is on a high plain in the Rockies or the Sierras, or New Mexico, it would be operating against reduced air resistance. It would seem to me that you might be able to get to orbit in a single stage this way. Do you think?

  28. “””””””I do agree though, Ecuador, Kenya and Tibet are far better prospects, though hawaii coul be OK too.”””””””

    OK, I know we’re just speculating and ruminating here, but forgive me for injecting a dose of reality:

    Kenya implies Mt. Kilimanjaro. Ain’t no way that Kilimanjaro or any similar Kenyan mountains would be allowed to be used for such a purpose. Ecuador is politically problematic. Tibet? Sure, unless you’re Richard Gere, I can see China allowing or building facilities for such launches if they find it to their benefit.

  29. “”””””””Mt Logan at 20000ft has a roughly 35 degree western flank dropping to about 10000 ft. Though it is pretty close to alaska.””””””

    Owe. 20,000 ft.? So much for my knowledge of N. American geography!

  30. Tim says:

    A while back I looked into Quito in Equador as an anchor site for a space elevator, and I realised something I don’t think has been mentioned yet; places up mountains are really difficult to get to. Quito for instance has an airport with an incredibly dangerous approach located right in the middle of the city, one railway that keeps getting washed out, and another that hugs the side of mountains all the way up from Guayaquil (the main coastal citycoastal city), if it still exists. I suspect places like Kenya are in a similar situation.

    A bit OT here, but does anyone know if a case can be made for using launch ramps and launching systems for commercial aircraft? I figure it means you can size the engines for cruise and landing rather than takeoff. If catapaulting commercial aircraft were viable, you would have more of a market for all the tech your developing, and once someone pays you to build a few, your choice of potential launch sites increases substantially if the commercial system is compatible with the sled.

    One final thing; how would you contain the lauch sled? As far as I can tell it just goes flying off the end of the ramp at high speed and low altitude, which sounds hairy.

  31. Robert Lynn says:

    looking at their politics ecuador may not be on, but tibet is a definite go.

    Having been there a year and a half ago it is a fascinating landscape, vast, arid and largely uninhabited with just about the best solar influx of anywhere in the world (solar panels sold by street vendors). Even the valley floors are 2.5-3 miles up.

    It is difficult to impress on westerners the incredible scale of infrastructural engineering that is going on in china. They would knock off a civil engineering challenge like this in very short order at low cost if their government got it in their head to do so.

    Given their space aspirations it is only a matter of time before they wake up and realise what an incredible asset they have in Tibet for space access with easy vehicle access to 20000ft or more. Leaving nationalism aside, they would be the best prospect for getting such a project done.

    Nepal also has some good mountains but is a massive infrastructural cockup and a generally failing country due to excessive population growth, a pity with Kangchenjunga at 8500m (28000ft) on the nepal/india border. Their low labour costs and altitude adjusted physiology would help get the job done very cheaply.

    A 3000ft ‘radiomast on steroids’ on any of the hundred or so 14000ft+ peaks in the US would be a good start. 6g gives mach1, and can use a simple falling weight on a pulley system to drive it. Greater accelerations for humans are also feasible, perhaps up to 15 or 20 g for a few seconds, particularly if in a water bath.

    Launch a partially fuelled centaur upper stage on this and you can basically do ssto to ISS. Now if we could just figure out how to get it back down for reuse.

  32. john hare says:

    I just read an article on launch lasers before seeing Tims’ comment.

    A few years ago I briefly discussed using lasers to augment rockets with Jordan Kare. My thought was that the laser could hit the opaque to that wavelength rocket exhaust to increase the Isp and thrust of a chemical rocket. Laser afterburning in the expansion nozzle to increase the exit temperature without further chemical reactions. My thought was that each percent of Isp and thrust gain by laser afterburning would be a percent more allowable GLOW and payload. The lasers could be incrementally increased in size and efficiency to produce payload gains without having to build your own rockets. He said such things had been “looked into”.

    Crossbreeding that idea with Tims’, laser afterburners at commercial airports could cut the time and fuel required for the airliners to accelerate and climb out. There would be another vehicle on the ramp every minute or three to give a commercially interesting ROI. Hundreds of uses per day per unit would ramp up the demand fairly rapidly. Then COTS lasers would be available for space launch.

    Doubling the temperature in the rocket exhaust would increase the Isp and thrust by 40%. 40% performance increase in the unchanged rocket engine allows higher expansion ratio at sea level which gives higher performance even beyond the laser range. By allowing more GLOW, much more payload can be sent by the same vehicle. It can start with a single percent performance increase to reduce up front costs.

  33. anon says:

    not to be a schmuck but a days work in POST would show
    this to not be a sound idea. Every optimized trajectory waits
    until you are out of the thick atmosphere before adding
    speed downrange.

    The Draglosses are horrific in thick atmosphere, and every
    program that’s tried tricks to get around it has failed.

    shining lasers sounds cool until you realize that small
    aiming errors will endanger the vehicle. Cool idea but
    unlikely to work reliably and if you put any error rates in
    say 5%, you just took your mission reliability rate and
    quadrupled the failures.

    unfortunately, orbital launch is a game without margin,
    and adding risk and reducing reliability versus the
    standard game of bigger tanks, is just not a winning
    strategy.

  34. john hare says:

    Anon,

    So your point is that we should never look at any possible means of improving the status quo?

  35. David Summers says:

    Anon has some points – though personally I consider such things challenges, not limitations! I often learn a lot by figuring out the assumptions behind a person that claims “it cannot be done!”

    Take the statement that rockets like to go straight up, why is that and at what point does it make sense to fly horizontally on wings for part of the way?

    As an example, gravity losses at 9.8m/s per second. You can trade gravity losses for drag losses at your L/D ratio. For example, while in the lower atmosphere you might have a L/D ratio of 6 – so if you can take a 30 second vertical climb and convert it to a less than 180 second aerodynamic climb, you have a net win.

    The problem, I believe, is that so little of your time is spent in the lower atmosphere that it makes no sense to add any additional mass to the rocket to make that portion easier. But that is the assumption – that you must add mass (and thereby screw up the overall performance) in order to do better at the lower atmosphere stuff. The laser does not require that, for example (though the safety issues would need to be addressed). Other ways of addressing that concern also exist – in fact, my company is working on one!

  36. john hare says:

    David,

    I took the tone of anon to mean that none of us had thought it through. If it had been you saying about the same thing, I would have responded differently with facts, numbers, or a retraction when you prove me wrong. (again)

    His point about using POST to prove that it is a bad idea ignores that a turn vertical is specifically suggested by several of us.

    The drag losses are addressed by a simple observation of the velocities involved compared to other vehicles. We were discussing adding 100 m/s or less at the start of the launch of a very slowly accelerating vehicle. The 100 m/s would still leave it slower than the shuttle at all altitudes after the first 20 seconds or so, which is very low subsonic.

    There are several professionals working on laser and other beamed energy proposals that have the aiming problems addressed. 5% aiming losses that he suggests would be criminal negligence. Just because I can’t build the system doesn’t mean that Jordan Kare or Leik Myrabo are incompetent.

    His last paragraph is dinospace lecture. I don’t respond well to that.
    I do apologize to you and any other real people that feel that the reply was inappropriate.

  37. Robert Lynn says:

    Another way of doing the vertical catapult launch cheaply:

    Find a deep valley; any place with two peaks up to a few miles apart and a maybe 3000ft valley in between would be good.
    String a very strong cable between them.

    Mount a pulley on the cable above the deepest part of the valley, this is your catapult’s pulling point. Use huge weight on a pulley block as the driver. You can choose the orientation of the boost to be anything between say vertical and maybe 30 degrees from horizontal.

    Perhaps the best approach would be a strengthened stratospheric blimp or balloon capable of lifting a light spectra or PBO rope connected to a winch on the ground through a pulley on the balloon and back to the launch vehicle.

    The winch on the ground first pulls up a stronger heavier winching cable that may weigh enough that the balloon starts to sink. Once this heavy cable is up the winch then ramps up pull massively to hoist and accelerate the LV off the ground and up into the stratosphere. At this point the balloon starts to sink quite quickly.

    The balloon can be built with a large integral parachute to increase drag when pulled down.

    This gives the overall ideal result of perhaps mach 2 to mach 3 catapult boost capability to an altitudes as high as maybe 100000 feet, with reasonably gentle acceleration and relatively low dynamic pressures. It is quiet, easily scalable, and not geography dependant and could be operated almost anywhere away from major air-routes with relatively low costs (though it will require a large impulse steam turbine or some-such to power the ground winch).

    The aerostat could have fuel and lifting gas replenished via the winch, and should be high enough to largely avoid the jet stream.

    Should be do-able for perhaps a hundred million (depending on scale), and though it will probably have higher operating costs it could reduce delta V requirements to around the 7.5-8km/s mark, making ‘SSTO’ RLV’s reasonably practical with an existing upper stage engines like the RL10.

    How could any air launch carrier aircraft development compete with this?

  38. David Summers says:

    Actually, Robert, that is very similar to an idea I had a while back for a launch assist of a small vehicle. Use a pair of small rockets to launch a large inflatable parachute to 60,000 feet (20km) or so. The rockets are each carrying a pulley – one side is attached to a large winch, the other side is attached to the launch vehicle. The small rockets go up and deploy the parachutes; then the winch pulls the launch vehicle up to say 45,000 feet (15km) at 200 m/s. The launch vehicle then starts its engines and flies off.

    The advantage is that your “first stage” is very simple to design, cheap to build, can be deployed quickly, and is recoverable (it is attached to the winch with a parachute out, after all). Unfortunately, as a first stage it is somewhat limited in performance – it won’t get you too much closer to orbit than you were. I still keep it in my back pocket, though, in case of a really bad performance miss.

    But the real reason I was looking into it was that it gives a vertical takeoff vehicle continuous abort capabilities – your parachutes are deployed at liftoff, after all.

  39. David Summers says:

    On laser assisted launch – if you could do that without modifying the vehicle that would be a no-brainer. Even if it only helped to a few thousand feet, optimizing engines for a higher altitude is always a win – we already take our engines to the raggedy edge of flow separation now!

    In that vane – how about this idea: Two rocket engines, with the exhausts slightly canted away from each other. You seed the exhaust to make it conductive, and then run electrical power up one exhaust and down the other! Self guided thrust augmentation power delivery!

    ;-}

  40. Ah yes, Maggie! Fireball XL-5.

    Cool and inspired that show was.

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